Thursday, April 4, 2013

Downhill creep or flow on the floor of Vitello?

Southern slope of a fracture developed in the floor of Vitello crater, on the south side of Mare Humorum. Downward slope is toward upper left in a 640 meter wide field of view centered on 30.214°S, 322.352°E, LROC NAC M1101460425L, LRO orbit 14652, September 5, 2012; angle of incidence 31.65° over 0.64 meters resolution, from 61.86 km [NASA/GSFC/Arizona State University].

Hiroyuki Sato
LROC News System

Vitello crater is a floor-fractured crater (42.5 km in diameter), located at the south edge of Mare Humorum.

As seen in the LROC Wide Angle Camera (WAC) context view further down, there is a circular network of fractures, with numerous branches, throughout the crater floor.

The opening images (above and immediately below) highlights a portion of north facing slopes inside one of these fractures (yellow box and arrow).

Full with of LROC NAC M1101460425L, from the corrected exploration link at the bottom of this post. The yellow square encompasses the area within the LROC Featured Image, released April 4, 2013 [NASA/GSFC/Arizona State University].

The dark materials on the floor of the crater partially cover the upper part of this fracture. The dark materials extend from the bottom right to upper left and are detoured around of a large boulder (30 by 20 meters) at the center of opening image, indicating that these materials flowed down the slope. With occasional events of slope failures or meteorite impacts, they might have flowed at once or little by little over a long period of time. But of what is this dark material composed?

The origin of floor-fractured craters on the Moon is still under discussion, but volcanic intrusions are suspected, and some of the fractures are associated with Dark Mantle Deposits (DMD), that are likely pyroclastic in origin. In Vitello crater, no clear DMD have been documented. But since the circular cracks are well developed in this crater, pyroclastics or any low reflectance materials of volcanic origin might have covered the fractured floor surface, supplying the dark materials flowing into the open cracks as seen in the opening image.

Vitello crater and surrounding areas in LROC WAC monochrome (604nm) mosaic (70 meters per pixel) centered on 30.393°S, 322.43°E, stitched from three LROC WAC observations, from three sequential orbital passes, February 6, 2010, from just above 50 km altitude. The locations of area in the LROC Featured Image (yellow arrow) is indicated once again [NASA/GSFC/Arizona State University].

Explore the slopes of the floor-fractured crater on the Moon in full NAC frame yourself, HERE.